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Rose Bengal Immobilized on Cellulose Paper for Sustainable Visible‐Light Photocatalysis
No full textInternational audienceThis work reports the heterogenization of Rose Bengal dye on simple cellulose paper sheets (Cell-RB) through copper-catalyzed azide-alkyne click ligation. The photocatalytic properties of Cell-RB under green LED irradiation were evaluated in a series of dehydrogenative transformations for the functionaliza-tion of N-aryltetrahydroisoquinolines and quinoxalin-2(1H)ones. The excellent photocatalytic activities observed, associated to the ease of recovery with simple tweezers, highlight the strong assets of Cell-RB with respect to traditional homogeneous organic photocatalysts
Relaxed-inertial proximal point algorithms for problems involving strongly quasiconvex functions
No full textInternational audienceIntroduced in the 1970's by Martinet for minimizing convex functions and extended shortly afterwards by Rockafellar towards monotone inclusion problems, the proximal point algorithm turned out to be a viable computational method for solving various classes of optimization problems, in particular with nonconvex objective functions.We propose first a relaxed-inertial proximal point type algorithm for solving optimization problems consisting in minimizing strongly quasiconvex functions whose variables lie in finitely dimensional linear subspaces. The method is then extended to equilibrium problems where the involved bifunction is strongly quasiconvex in the second variable.Possible modifications of the hypotheses that would allow the algorithms to solve similar problems involving quasiconvex functions are discussed, too. Numerical experiments confirming the theoretical results, in particular that the relaxed-inertial algorithms outperform their ``pure'' proximal point counterparts, are provided, too
Relaxed-inertial proximal point algorithms for problems involving strongly quasiconvex functions
No full textInternational audienceIntroduced in the 1970's by Martinet for minimizing convex functions and extended shortly afterward by Rockafellar towards monotone inclusion problems, the proximal point algorithm turned out to be a viable computational method for solving various classes of optimization problems, in particular with nonconvex objective functions.We propose first a relaxed-inertial proximal point type algorithm for solving optimization problems consisting in minimizing strongly quasiconvex functions whose variables lie in finitely dimensional linear subspaces. The method is then extended to equilibrium problems where the involved bifunction is strongly quasiconvex in the second variable.Possible modifications of the hypotheses that would allow the algorithms to solve similar problems involving quasiconvex functions are discussed, too. Numerical experiments confirming the theoretical results, in particular that the relaxed-inertial algorithms outperform their ``pure'' proximal point counterparts, are provided, too
An accelerated level-set method for inverse scattering problems
No full textInternational audienceWe propose a rapid and robust iterative algorithm to solve inverse acoustic scattering problems formulated as a PDE constrained shape optimization problem. We use a level-set method to represent the obstacle geometry and propose a new scheme for updating the geometry based on an adaptation of accelerated gradient descent methods. The resulting algorithm aims at reducing the number of iterations and improving the accuracy of reconstructions. To cope with regularization issues, we propose a smoothing to the shape gradient using a single layer potential associated with ik where k is the wave number. Numerical experiments are given for several data types (full aperture, backscattering, phaseless, multiple frequencies) and show that our method outperforms a non accelerated approach in terms of convergence speed, accuracy and sensitivity to initial guesses
Experimental Studies of Autonomous Sailing With a Radio Controlled Sailboat
No full textInternational audienceAutonomous sailing has attracted many interests from both industry and academy due to its great potential in oceanography, research and education. Worldwide researchers have developed various kinds of unmanned sailboat platforms for their specific research purposes and applications. However, most of these autonomous sailing platforms are rather complex to build and to program. The aim of this study is to propose, to build, and to test a new compact sailboat platform using a unique combination of a 1-m class radio controlled model sailboat, a Raspberry Pi 4, a Navio2 board, and a Calypso ultrasonic solar-powered anemometer. The proposed new sailboat platform makes full use of the agility of the racing model boat with minimal mechanical adjustments as the system does not use electrical wires to connect with additional sensors and a mechanical anemometer. The software architecture of the proposed new sailboat platform is also simplified as it involves only Python programming for the Raspberry Pi 4. The experimental results have demonstrated the feasibility as well as the functionality of the proposed new sailboat platform to conduct autonomous sailing operations successfully and it could become one of the most accessible, generic and flexible autonomous sailing platforms for advanced research and education in robotics, autonomous systems, and artificial intelligence
IWST 2022: International Workshop on Smalltalk Technologies 2022
No full textInternational audienceThe International Smalltalk Technologies Workshop (IWST) is a forum around advances or experience in Smalltalk, bringing together Smalltalk practitioners since 2009. The IWST aims to stimulate discussion and exchange of ideas on all aspects of Smalltalk, both theoretical and practical. IWST is a co-located event with the annual European Smalltalk User Group (ESUG) conference. The 2022 edition of IWST was held in Novi Sad, Serbia, July 24-26, with Lam Research Corporation as a sponsor
International practice of capacity building in engineering education: a comparative case study
No full textInternational audienceCapacity building is a corner stone for having well prepared and effective teaching staff in engineering education. Despite the importance of capacity building in engineering education, there is relatively little research on this topic. In this paper,we address this gap by reporting on an international comparative study on capacity building practices in university-level engineering education. We examine how capacity building is organised in seven European institutions (in Belgium, Finland, France, Germany, Hungary, Sweden, UK) and Australia, based on institutional education policies and practices. We compare the preparation of teaching staff, their initial training, and continuing capacity building activities throughout their careers. To do this, we applied a qualitative approach, collecting data through (1) a structured questionnaire answered by the members of the SEFI SIG on Capacity building and (2) written notes produced during an international workshop on capacity building at the 2021 SEFI conference. We then conducted a comparative case study, exploring similarities and differences between incentives for permanent academic staff to engage in capacity building, how capacity building is organised, and at what point in their careers staff engage in it. Our findings indicate very diverse approaches, rules and practices as well as different obstacles and challenges for engineering education. The outcomes of our study can be used by policy makers to inform capacity building practices and engineering education in HEIs (Higher Education Institutions), and our questionnaire provides a tool for monitoring and reporting practices throughout the sector
Limiting amplitude principle and resonances in plasmonic structures with corners: numerical investigation
No full textInternational audienceThe limiting amplitude principle states that the response of a scatterer to a harmonic light excitation is asymptotically harmonic with the same pulsation. Depending on the geometry and nature of the scatterer, there might or might not be an established theoretical proof validating this principle. In this paper, we investigate a case where the theory is missing: we consider a two-dimensional dispersive Drude structure with corners. In the non lossy case, it is well known that looking for harmonic solutions leads to an ill-posed problem for a specific range of critical pulsations, characterized by the metal’s properties and the aperture of the corners. Ill-posedness is then due to highly oscillatory resonances at the corners called black-hole waves. However, a time-domain formulation with a harmonic excitation is always mathematically valid. Based on this observation, we conjecture that the limiting amplitude principle might not hold for all pulsations. Using a time-domain setting, we propose a systematic numerical approach that allows to give numerical evidences of the latter conjecture, and find clear signature of the critical pulsa-tions. Furthermore, we connect our results to the underlying physical plasmonic resonances thatoccur in the lossy physical metallic case
A posteriori error estimates via equilibrated stress reconstructions for contact problems approximated by Nitsche's method
No full textInternational audienceWe present an a posteriori error estimate based on equilibrated stress reconstructions for the finite element approximation of a unilateral contact problem with weak enforcement of the contact conditions. We start by proving a guaranteed upper bound for the dual norm of the residual. This norm is shown to control the natural energy norm up to a boundary term, which can be removed under a saturation assumption. The basic estimate is then refined to distinguish the different components of the error, and is used as a starting point to design an algorithm including adaptive stopping criteria for the nonlinear solver and automatic tuning of a regularization parameter. We then discuss an actual way of computing the stress reconstruction based on the Arnold-Falk-Winther finite elements. Finally, after briefly discussing the efficiency of our estimators, we showcase their performance on a panel of numerical tests